Typically, vacuum cleaners use a vacuum cleaner head having a dirty air inlet which is in flow communication with a source of suction (e.g. a motor driven fan unit). When the vacuum cleaner is turned on, the suction source creates a low pressure area which draws air into the dirty air inlet. Dirt particles and the like are entrained in the air flow and transported by the air flow to a dirt separation mechanism provided with the vacuum cleaner. In order to assist the entrainment of dirt particles and the like in the air stream entering the dirty air inlet, an agitator (e.g. a rotatably mounted brush) is provided. The rotation of the brush agitates the surface (e.g. carpet) over which the vacuum cleaner head travels. This agitation disturbs the dirt which is in the carpet so that it may more easily be entrained in the air entering the dirty air inlet.
It is know in the art to mount the brush in a fixed position in the vacuum cleaner head. In order to accommodate different surfaces (eg. carpets having different pile heights), it is known to manually adjust the height of the brush with respect to the dirty air inlet. Automatic adjustment controls for adjusting the height of the brush with respect to the dirty air inlet are also know. One example is shown in U.S. Pat. No. 2,614,283 (Thornwald). According to this patent, a pivotally mounted nap engaging structure is provided. The structure is pivoted about a pivot point positioned rearward of the brush.